1. Field of the Invention
The present invention relates to a system and a method for controlling engine cooling fan activation based on intake manifold air temperature and time in an exhaust gas recirculation (EGR) system.
2. Background Art
Internal combustion engines, and in particular, compression ignition (or diesel) engines have a wide variety of applications including passenger vehicles, marine vessels, earth-moving and construction equipment, stationary generators, and on-highway trucks, among others. However, due to the loads carried by the vehicles and the size of the machinery that utilize internal combustion engines, internal combustion engines (e.g., diesel engines) generate a great deal of heat during operation.
The heat generated by internal combustion engines has also increased due to the addition of exhaust gas recirculation (EGR) systems into the engines. EGR systems recirculate exhaust into the intake air stream of the engine, thereby reducing oxides of nitrogen that are formed when temperatures in the combustion chamber of the engine get too hot. Although the EGR systems help to reduce exhaust emissions that cause smog, EGR systems cause the intake manifold air temperatures of the engine to increase.
Some conventional systems and methods for controlling the heat within internal combustion engines implement a fixed speed, a variable speed, or multiple engine cooling fans that move air over a radiator where engine coolant flows and is cooled by the air movement. A conventional electronic control unit operates the fan in accordance with received fan request signals, turning the fan on or off and adjusting the fan speed depending on the temperature within the engine (e.g., in response to engine coolant temperature). However, some of the fan requests are unnecessary due to short increases in temperature caused by quick changes in engine load (e.g., small rolling hills, idle to rapid acceleration operation, intermittent workpiece characteristics for power takeoff driven applications, etc.). The unnecessary fan requests can cause the engine speed and output torque to fluctuate erratically. The engine speed and torque fluctuations can cause undesirable vehicle (or machinery) speed variations, noise and vibration, reduced fuel economy, etc.
Thus, there exists a need and an opportunity for an improved system and an improved method for engine cooling fan control. The present invention may implement an improved system and an improved method for controlling cooling fan activation and fan speed based on intake manifold air temperature and time in an EGR system. The present invention may minimize the unnecessary fan request signals as sent by some conventional approaches and, thus, may provide improved efficiency and noise control for operation of the fan activation system. Furthermore, the present invention may provide more flexible fan control parameters (i.e., a greater number of modes of engine cooling fan control) when compared to conventional approaches.